In the related art, there is a sheet having parts of which physical characteristics such as thicknesses or materials are different from each other in the sheet. In a case of forming an image on such a sheet (hereinafter, referred to as a “hybrid sheet”) having a plurality of parts of which the physical characteristics are different from each other as described above, there is a case where image forming quality is reduced because of the non-uniformity. The reason is as described below. In forming the image on the hybrid sheet, an image forming condition is determined according to a condition of a physical characteristics (for example, the thickness and the material) of any of the parts. In this case, there may be a case where the determined image forming condition and an optimal image forming condition for another part do not coincide with each other.